Dual mode serial transmission apparatus and method for switching mode thereof

Abstract

A dual mode serial transmission apparatus and method for switching a mode thereof are provided. The dual mode serial transmission apparatus includes a first and second current sources, a first and second inverting circuits, a differential pair and a resistor string. The first inverting circuit receives a mode selecting signal or a first data transmission signal, the second inverting circuit receives the mode selecting signal or a second data transmission signal. First and second load terminals of the differential pair are respectively coupled to the first and second inverting circuits. A common terminal of the differential pair is coupled to the second current source. First and second differential input terminals receive the mode selecting signal or respectively receive the first and second data transmission signals. The resistor string is coupled in series between output terminals of the first and second inverting circuits.

What is claimed is: 
     
       1. A dual mode serial transmission apparatus, comprising:
 a first current source; 
 a first inverting circuit, coupled to the first current source, and receiving a mode selecting signal or a first data transmission signal; 
 a second inverting circuit, coupled to the first current source, and receiving the mode selecting signal or a second data transmission signal; 
 a second current source; and 
 a differential pair, having a first and a second load terminals respectively coupled to the first inverting circuit and the second inverting circuit, a common terminal being coupled to the second current source, and a first and second differential input terminals receiving the mode selecting signal or respectively receiving the first and second data transmission signals, 
 wherein when the first and second inverting circuits respectively receive the first and second data transmission signals, the differential pair receives the mode selecting signal, and when the first and second inverting circuits receive the mode selecting signal, the differential pair receives the first and second data transmission signals. 
 
     
     
       2. The dual mode serial transmission apparatus as claimed in  claim 1 , comprising:
 a resistor string, having a first resistor and second resistor, wherein the first and the second resistors are coupled in series between an output terminal of the first inverting circuit and an output terminal of the second inverting circuit. 
 
     
     
       3. The dual mode serial transmission apparatus as claimed in  claim 1 , wherein under a first operation mode, the first and second inverting circuits respectively receive the first and second data transmission signals, and the first and second differential input terminals of the differential pair receive the mode selecting signal, and under a second operation mode, the first and second inverting circuits receive the mode selecting signal, and the first and second differential input terminals of the differential pair respectively receive the first and second data transmission signals. 
     
     
       4. The dual mode serial transmission apparatus as claimed in  claim 3 , wherein the first inverting circuit comprises:
 a first switch, coupled in series between the first current source and the resistor string, wherein the first switch is turned on or cut off according to the mode selecting signal or the first data transmission signal; and 
 a second switch, coupled in series between the resistor string and the first load terminal, wherein the second switch is turned on or cut off according to the mode selecting signal or the first data transmission signal; 
 the second inverting circuit comprises: 
 a third switch, coupled in series between the first current source and the resistor string, wherein the third switch is turned on or cut off according to the mode selecting signal or the second data transmission signal; and 
 a fourth switch, coupled in series between the resistor string and the second load terminal, wherein the fourth switch is turned on or cut off according to the mode selecting signal or the second data transmission signal. 
 
     
     
       5. The dual mode serial transmission apparatus as claimed in  claim 4 , wherein under the second operation mode, the first and third switches are cut off according to the mode selecting signal, and the second and fourth switches are turned on according to the mode selecting signal. 
     
     
       6. The dual mode serial transmission apparatus as claimed in  claim 3 , wherein the differential pair comprises:
 a fifth switch, coupled between the first load terminal and the common terminal, wherein the fifth switch is turned on or cut off according to the mode selecting signal or the first data transmission signal; and 
 a sixth switch, coupled between the second load terminal and the common terminal, wherein the sixth switch is turned on or cut off according to the mode selecting signal or the second data transmission signal. 
 
     
     
       7. The dual mode serial transmission apparatus as claimed in  claim 6 , wherein under the first operation mode, the fifth and the sixth switches are cut off according to the mode selecting signal. 
     
     
       8. The dual mode serial transmission apparatus as claimed in  claim 3 , wherein under the second operation mode, common coupling terminals of the first and the second resistors are applied with an operating power of the dual mode serial transmission apparatus. 
     
     
       9. The dual mode serial transmission apparatus as claimed in  claim 3 , wherein the first operation mode is a first low voltage differential signal transmission mode, and the second operation mode is a current mode logic. 
     
     
       10. The dual mode serial transmission apparatus as claimed in  claim 3 , wherein under the first operation mode, an intersection voltage generated when the first and second data transmission signals are transited is lower than a first predetermined voltage value, and under the second operation mode, the intersection voltage is higher than a second predetermined voltage value, and the first predetermined voltage value is smaller than or equal to the second predetermined voltage value. 
     
     
       11. The dual mode serial transmission apparatus as claimed in  claim 1 , further comprising:
 a first pre-driver, coupled on a path which the first inverting circuit receives the mode selecting signal or the first data transmission signal; 
 a second pre-driver, coupled on a path which the second inverting circuit receives the mode selecting signal or the second data transmission signal; 
 a third pre-driver, coupled on a path which the first differential input terminal receives the mode selecting signal or the first data transmission signal; and 
 a fourth pre-driver, coupled on a path which the second differential input terminal receives the mode selecting signal or the second data transmission signal. 
 
     
     
       12. A method for switching mode in the dual mode serial transmission apparatus as claimed in  claim 1 , the method comprising:
 providing the mode selecting signal to the differential pair under a first operation mode, for conducting a connection path between the first inverting circuit and the common terminal by the differential pair, and conducting a connection path between the second inverting circuit and the common terminal by the differential pair; 
 providing the mode selecting signal to the first and the second inverting circuits under a second operation mode, for conducting a connection path between the first load terminal and the output terminal of the first inverting circuit, and conducting a connection path between the second load terminal and the output terminal of the second inverting circuit; 
 respectively providing the first and the second data transmission signals to the first and the second inverting circuits under the first operating mode; and 
 respectively providing the first and the second data transmission signals to the first and the second differential input terminals of the differential pair under the second operation mode. 
 
     
     
       13. The method for switching mode as claimed in  claim 12 , wherein the first operation mode is a first low voltage differential signal transmission mode, and the second operation mode is a current mode logic. 
     
     
       14. The method for switching mode as claimed in  claim 12 , wherein under the first operation mode, an intersection voltage generated when the first and second data transmission signals are transited is lower than a first predetermined voltage value, and under the second operation mode, the intersection voltage is higher than a second predetermined voltage value, and the first predetermined voltage value is smaller than or equal to the second predetermined voltage value.